It is known that supply of LP gas is based on import from gas producing countries and domestic production as by-product in the course of producing petroleum products. Petroleum refining terminals and import terminals for storing LP gas carried from gas producing countries by tankers are respectively referred to as primary terminals. LP gas is loaded into domestic vessels and/or tank trucks in the primary terminals and is shipped to secondary terminals located on the coast or inland as hub terminals for LP gas transportation. Further, LP gas carried to the secondary terminals is transported to LP gas filling stations in various locations, i.e., delivery branches, and is then injected into gas cylinders (gas canisters) in the delivery branches.
The gas cylinders, filled with LP gas in the respective filling stations, are delivered to customers' places such as residential houses, apartment houses and work places by deliverymen. Empty gas cylinders in the customers' places are replaced with full gas cylinders, and are brought back to the respective filling stations. In each filling station, a fixed delivery area is assigned to each deliveryman as an area of which he/she is in charge. Each deliveryman is given delivery tickets to be delivered to customers' places within his/her responsible delivery area in 2 to 10 days.
The delivery tickets are created by a delivery manager. First, the amount of LP gas remaining in each gas cylinder is predicted based on a past gas usage history of each customer, a meter indication of a gas meter in each customer's place, a delivery history and so forth, and the next delivery due date of each gas cylinder is determined. The number of gas cylinders to be delivered in 2 to 10 days is determined by accumulating the number of gas cylinders of all the customers within the delivery area of which each deliveryman is in charge.
In replacing a gas cylinder based on a delivery ticket, a deliveryman fills in the respective items of the delivery ticket including a replacement date, a meter indication on the date, a cylinder number and a safety inspection. When a daily delivery work is finished, delivery tickets are handed in to the delivery manager. The delivery manager checks if each delivery ticket returned to him/her includes incomplete items, and then, stores each checked delivery ticket as data for calculating the next delivery due date. Under the aforementioned mechanism, a system for enhancing efficiency in delivery of a gas cylinder has been proposed (see PTL 1).
As disclosed in PTL 1, a system for enhancing efficiency in delivery of a gas cylinder has conventionally existed, but has had a problem that in delivering a gas cylinder, it has been impossible for the system to determine a delivery date of the gas cylinder such that gas delivery can be stably supplied and further the remaining amount of gas to be brought back can be reduced.